package org.terrier.terms;

/*

Porter stemmer in Java. The original paper is in

    Porter, 1980, An algorithm for suffix stripping, Program, Vol. 14,
    no. 3, pp 130-137,

See also http://www.tartarus.org/~martin/PorterStemmer

History:

Release 1

Bug 1 (reported by Gonzalo Parra 16/10/99) fixed as marked below.
The words 'aed', 'eed', 'oed' leave k at 'a' for step 3, and b[k-1]
is then out outside the bounds of b.

Release 2

Similarly,

Bug 2 (reported by Steve Dyrdahl 22/2/00) fixed as marked below.
'ion' by itself leaves j = -1 in the test for 'ion' in step 5, and
b[j] is then outside the bounds of b.

Release 3

Considerably revised 4/9/00 in the light of many helpful suggestions
from Brian Goetz of Quiotix Corporation (brian@quiotix.com).

Release 4

*/

import java.io.*;

/**
* Stemmer, implementing the Porter Stemming Algorithm. By Martin Porter.
*
* The Stemmer class transforms a word into its root form.  The input
* word can be provided a character at time (by calling add()), or at once
* by calling one of the various stem(something) methods.
* 
* @since 3.0
*/

public class PorterStemmer extends StemmerTermPipeline
{  
	protected char[] b;
	protected int i,     /* offset into b */
	            i_end, /* offset to end of stemmed word */
	            j, k;
	protected static final int INC = 50;
	                  /* unit of size whereby b is increased */
	/**
	 * constructor
	 */
	public PorterStemmer()
	{  b = new char[INC];
	   i = 0;
	   i_end = 0;
	}
	/** 
	 * Constructs an instance of PorterStemmer.
	 * @param next
	 */
	public PorterStemmer(TermPipeline next)
	{
	   super(next);
	   b = new char[INC];
	   i = 0;
	   i_end = 0;
	}
	
	/**
	 * Add a character to the word being stemmed.  When you are finished
	 * adding characters, you can call stem(void) to stem the word.
	 */
	
	public void add(char ch)
	{  if (i == b.length)
	   {  char[] new_b = new char[i+INC];
	      for (int c = 0; c < i; c++) new_b[c] = b[c];
	      b = new_b;
	   }
	   b[i++] = ch;
	}
	
	
	/** Adds wLen characters to the word being stemmed contained in a portion
	 * of a char[] array. This is like repeated calls of add(char ch), but
	 * faster.
	 */
	
	public void add(char[] w, int wLen)
	{  if (i+wLen >= b.length)
	   {  char[] new_b = new char[i+wLen+INC];
	      for (int c = 0; c < i; c++) new_b[c] = b[c];
	      b = new_b;
	   }
	   for (int c = 0; c < wLen; c++) b[i++] = w[c];
	}
	
	/**
	 * After a word has been stemmed, it can be retrieved by toString(),
	 * or a reference to the internal buffer can be retrieved by getResultBuffer
	 * and getResultLength (which is generally more efficient.)
	 */
	public String toString() { return new String(b,0,i_end); }
	
	/**
	 * Returns the length of the word resulting from the stemming process.
	 */
	public int getResultLength() { return i_end; }
	
	/**
	 * Returns a reference to a character buffer containing the results of
	 * the stemming process.  You also need to consult getResultLength()
	 * to determine the length of the result.
	 */
	public char[] getResultBuffer() { return b; }
	
	/* cons(i) is true <=> b[i] is a consonant. */
	
	protected final boolean cons(int _i)
	{  switch (b[_i])
	   {  case 'a': case 'e': case 'i': case 'o': case 'u': return false;
	      case 'y': return (_i==0) ? true : !cons(_i-1);
	      default: return true;
	   }
	}
	
	/* m() measures the number of consonant sequences between 0 and j. if c is
	   a consonant sequence and v a vowel sequence, and <..> indicates arbitrary
	   presence,
	
	      <c><v>       gives 0
	      <c>vc<v>     gives 1
	      <c>vcvc<v>   gives 2
	      <c>vcvcvc<v> gives 3
	      ....
	*/
	
	protected final int m()
	{  int n = 0;
	   int _i = 0;
	   while(true)
	   {  if (_i > j) return n;
	      if (! cons(_i)) break; _i++;
	   }
	   _i++;
	   while(true)
	   {  while(true)
	      {  if (_i > j) return n;
	            if (cons(_i)) break;
	            _i++;
	      }
	      _i++;
	      n++;
	      while(true)
	      {  if (_i > j) return n;
	         if (! cons(_i)) break;
	         _i++;
	      }
	      _i++;
	    }
	}
	
	/* vowelinstem() is true <=> 0,...j contains a vowel */
	
	protected final boolean vowelinstem()
	{  int _i; for (_i = 0; _i <= j; _i++) if (! cons(_i)) return true;
	   return false;
	}
	
	/* doublec(j) is true <=> j,(j-1) contain a double consonant. */
	
	protected final boolean doublec(int _j)
	{  if (_j < 1) return false;
	   if (b[_j] != b[_j-1]) return false;
	   return cons(_j);
	}
	
	/* cvc(i) is true <=> i-2,i-1,i has the form consonant - vowel - consonant
	   and also if the second c is not w,x or y. this is used when trying to
	   restore an e at the end of a short word. e.g.
	
	      cav(e), lov(e), hop(e), crim(e), but
	      snow, box, tray.
	
	*/
	
	protected final boolean cvc(int _i)
	{  if (_i < 2 || !cons(_i) || cons(_i-1) || !cons(_i-2)) return false;
	   {  int ch = b[_i];
	      if (ch == 'w' || ch == 'x' || ch == 'y') return false;
	   }
	   return true;
	}
	
	protected final boolean ends(String s)
	{  int l = s.length();
	   int o = k-l+1;
	   if (o < 0) return false;
	   for (int _i = 0; _i < l; _i++) if (b[o+_i] != s.charAt(_i)) return false;
	   j = k-l;
	   return true;
	}
	
	/* setto(s) sets (j+1),...k to the characters in the string s, readjusting
	   k. */
	
	protected final void setto(String s)
	{  int l = s.length();
	   int o = j+1;
	   for (int _i = 0; _i < l; _i++) b[o+_i] = s.charAt(_i);
	   k = j+l;
	}
	
	/* r(s) is used further down. */
	
	protected final void r(String s) { if (m() > 0) setto(s); }
	
	/* step1() gets rid of plurals and -ed or -ing. e.g.
	
	       caresses  ->  caress
	       ponies    ->  poni
	       ties      ->  ti
	       caress    ->  caress
	       cats      ->  cat
	
	       feed      ->  feed
	       agreed    ->  agree
	       disabled  ->  disable
	
	       matting   ->  mat
	       mating    ->  mate
	       meeting   ->  meet
	       milling   ->  mill
	       messing   ->  mess
	
	       meetings  ->  meet
	
	*/
	
	protected final void step1()
	{  if (b[k] == 's')
	   {  if (ends("sses")) k -= 2; else
	      if (ends("ies")) setto("i"); else
	      if (b[k-1] != 's') k--;
	   }
	   if (ends("eed")) { if (m() > 0) k--; } else
	   if ((ends("ed") || ends("ing")) && vowelinstem())
	   {  k = j;
	      if (ends("at")) setto("ate"); else
	      if (ends("bl")) setto("ble"); else
	      if (ends("iz")) setto("ize"); else
	      if (doublec(k))
	      {  k--;
	         {  int ch = b[k];
	            if (ch == 'l' || ch == 's' || ch == 'z') k++;
	         }
	      }
	      else if (m() == 1 && cvc(k)) setto("e");
	  }
	}
	
	/* step2() turns terminal y to i when there is another vowel in the stem. */
	
	protected final void step2() { if (ends("y") && vowelinstem()) b[k] = 'i'; }
	
	/* step3() maps double suffices to single ones. so -ization ( = -ize plus
	   -ation) maps to -ize etc. note that the string before the suffix must give
	   m() > 0. */
	
	protected final void step3() { if (k == 0) return; /* For Bug 1 */ switch (b[k-1])
	{
	    case 'a': if (ends("ational")) { r("ate"); break; }
	              if (ends("tional")) { r("tion"); break; }
	              break;
	    case 'c': if (ends("enci")) { r("ence"); break; }
	              if (ends("anci")) { r("ance"); break; }
	              break;
	    case 'e': if (ends("izer")) { r("ize"); break; }
	              break;
	    case 'l': if (ends("bli")) { r("ble"); break; }
	              if (ends("alli")) { r("al"); break; }
	              if (ends("entli")) { r("ent"); break; }
	              if (ends("eli")) { r("e"); break; }
	              if (ends("ousli")) { r("ous"); break; }
	              break;
	    case 'o': if (ends("ization")) { r("ize"); break; }
	              if (ends("ation")) { r("ate"); break; }
	              if (ends("ator")) { r("ate"); break; }
	              break;
	    case 's': if (ends("alism")) { r("al"); break; }
	              if (ends("iveness")) { r("ive"); break; }
	              if (ends("fulness")) { r("ful"); break; }
	              if (ends("ousness")) { r("ous"); break; }
	              break;
	    case 't': if (ends("aliti")) { r("al"); break; }
	              if (ends("iviti")) { r("ive"); break; }
	              if (ends("biliti")) { r("ble"); break; }
	              break;
	    case 'g': if (ends("logi")) { r("log"); break; }
	} }
	
	/* step4() deals with -ic-, -full, -ness etc. similar strategy to step3. */
	
	protected final void step4() { switch (b[k])
	{
	    case 'e': if (ends("icate")) { r("ic"); break; }
	              if (ends("ative")) { r(""); break; }
	              if (ends("alize")) { r("al"); break; }
	              break;
	    case 'i': if (ends("iciti")) { r("ic"); break; }
	              break;
	    case 'l': if (ends("ical")) { r("ic"); break; }
	              if (ends("ful")) { r(""); break; }
	              break;
	    case 's': if (ends("ness")) { r(""); break; }
	              break;
	} }
	
	/* step5() takes off -ant, -ence etc., in context <c>vcvc<v>. */
	
	protected final void step5()
	{   if (k == 0) return; /* for Bug 1 */ switch (b[k-1])
	    {  case 'a': if (ends("al")) break; return;
	       case 'c': if (ends("ance")) break;
	                 if (ends("ence")) break; return;
	       case 'e': if (ends("er")) break; return;
	       case 'i': if (ends("ic")) break; return;
	       case 'l': if (ends("able")) break;
	                 if (ends("ible")) break; return;
	       case 'n': if (ends("ant")) break;
	                 if (ends("ement")) break;
	                 if (ends("ment")) break;
	                 /* element etc. not stripped before the m */
	                 if (ends("ent")) break; return;
	       case 'o': if (ends("ion") && j >= 0 && (b[j] == 's' || b[j] == 't')) break;
	                                 /* j >= 0 fixes Bug 2 */
	                 if (ends("ou")) break; return;
	                 /* takes care of -ous */
	       case 's': if (ends("ism")) break; return;
	       case 't': if (ends("ate")) break;
	                 if (ends("iti")) break; return;
	       case 'u': if (ends("ous")) break; return;
	       case 'v': if (ends("ive")) break; return;
	       case 'z': if (ends("ize")) break; return;
	       default: return;
	    }
	    if (m() > 1) k = j;
	}
	
	/* step6() removes a final -e if m() > 1. */
	
	protected final void step6()
	{  j = k;
	   if (b[k] == 'e')
	   {  int a = m();
	      if (a > 1 || a == 1 && !cvc(k-1)) k--;
	   }
	   if (b[k] == 'l' && doublec(k) && m() > 1) k--;
	}
	
	/** Stem the word placed into the Stemmer buffer through calls to add().
	 * Returns true if the stemming process resulted in a word different
	 * from the input.  You can retrieve the result with
	 * getResultLength()/getResultBuffer() or toString().
	 */
	public void stem()
	{  k = i - 1;
	   if (k > 1) { step1(); step2(); step3(); step4(); step5(); step6(); }
	   i_end = k+1; i = 0;
	}
	
	/** Test program for demonstrating the Stemmer.  It reads text from a
	 * a list of files, stems each word, and writes the result to standard
	 * output. Note that the word stemmed is expected to be in lower case:
	 * forcing lower case must be done outside the Stemmer class.
	 * Usage: Stemmer file-name file-name ...
	 */
	public static void main(String[] args)
	{
	   char[] w = new char[501];
	   PorterStemmer s = new PorterStemmer();
	   for (int i = 0; i < args.length; i++)
	   try
	   {
	      FileInputStream in = new FileInputStream(args[i]);
	
	      try
	      { while(true)
	
	        {  int ch = in.read();
	           if (Character.isLetter((char) ch))
	           {
	              int j = 0;
	              while(true)
	              {  ch = Character.toLowerCase((char) ch);
	                 w[j] = (char) ch;
	                 if (j < 500) j++;
	                 ch = in.read();
	                 if (!Character.isLetter((char) ch))
	                 {
	                    /* to test add(char ch) */
	                    for (int c = 0; c < j; c++) s.add(w[c]);
	
	                    /* or, to test add(char[] w, int j) */
	                    /* s.add(w, j); */
	
	                    s.stem();
	                    {  String u;
	
	                       /* and now, to test toString() : */
	                       u = s.toString();
	
	                       /* to test getResultBuffer(), getResultLength() : */
	                       /* u = new String(s.getResultBuffer(), 0, s.getResultLength()); */
	
	                       System.out.print(u);
	                    }
	                    break;
	                 }
	              }
	           }
	           if (ch < 0) break;
	           System.out.print((char)ch);
	        }
	      }
	      catch (IOException e)
	      {  System.out.println("error reading " + args[i]);
	         break;
	      }
	   }
	   catch (FileNotFoundException e)
	   {  System.out.println("file " + args[i] + " not found");
	      break;
	   }
	}

	/* Stemmer implementation */
	/** {@inheritDoc} */
	public String stem(String s) {
		this.add(s.toCharArray(), s.length());
		this.stem();
		return this.toString();
	}
}

